A writing nib to be attached to a writing instrument such as a sign pen or marking pen for providing letters which are uniform in thickness from beginning to end regardless of the angle between the nib and the paper, should satisfy the following demands:
1. It should provide a nib having a fine diameter, since abrasion of the tip of said nib is inevitable.
2. A sufficient capillary action should be provided when writing. This can be attained by making the ink conduit very fine, but in order to maintain a sufficient amount of ink in said fine conduit to prevent "scratching", it is necessary to enlarge the total cross section of the conduit.
3. In order to provide a nib which is easy to write with, the tip portion of the nib should have a sufficient bending strength.
The applicant already has proposed writing instruments each provided with a writing nib of the above-mentioned type. In U.S. Pat. No. 3,614,247 the nib has a capillary conduit forming a snow flake shape in transverse cross section thereof. In U.S. Pat. No. 3,520,629 the nib has a capillary conduit forming a star shape in transverse cross section thereof.
However, these known nibs do not satisfy all of the above-mentioned demands (1), (2) and (3).